The field of the disclosure relates generally to communication systems and networks, and more particularly, to communications systems and networks employing non-orthogonal multiple access.
Conventional hybrid fiber-coaxial (HFC) architectures typically deploy fiber strands from an optical hub to a fiber node, and often many short coaxial or fiber strands to cover the shorter distances from the fiber nodes to a plurality of end users. Conventional Multiple Service Operators (MSOs) offer a variety of services, including analog/digital TV, video on demand (VoD), telephony, and high speed data internet, over these HFC networks, which utilize both optical fibers and coaxial cables, and which provide video, voice, and data services to the end user subscribers. HFC networks are known to include a master headend, and the optical fiber strands carry the optical signals between the headend, the hub, and the fiber node. Conventional HFC networks also typically include a plurality of coaxial cables to connect the fiber nodes to the respective end users, and to carry radio frequency (RF) modulated analog electrical signals.
The HFC fiber node converts optical analog signals from the optical fiber into the RF modulated electrical signals that are transported by the coaxial cables to the end users/subscribers. In the conventional HFC network, both the optical and electrical signals are analog, from the hub to the end user subscriber's home. Typically, a modem termination system (MTS) is located at either the headend or the hub, and provides complementary functionality to a modem of the respective end user.
The signal components of the conventional HFC fiber/coaxial cable links experience higher propagation attenuation at higher frequency. The attenuation increases over distance and this attenuation effect is particularly significant in coaxial cables. Thus, different users of the network will experience difference system performance at different distances from the fiber node, at different operation frequencies. Conventional HFC networks, however, implement orthogonal multiple access (OMA) techniques to allocate resources orthogonally in the frequency and time domains.
FIG. 1 is a graphical illustration depicting a conventional orthogonal multiple access (OMA) two-dimensional frequency-time-power distribution 100 of users 102. In the exemplary embodiment illustrated in FIG. 1, distribution 100 is depicted with respect to a conventional HFC network that implements a communication protocol such as the Data Over Cable Service Interface Specification (DOCSIS), or DOCSIS version 3.1 (D3.1). In this example, each of the several different users 102 are illustrated as occupying different frequency-time slots on (e.g., on a 2-D plane) and do not overlap with other users 102.
According to conventional OMA distribution 100, the OMA techniques of distribution 100 do not consider the respective variations experienced by users 102 according to the distance of a particular user 102 from the node, or the frequency slot at which that user 102 is operating. More particularly, the conventional OMA techniques do not optimize resource allocation based on these variations, thereby resulting in low spectral efficiency. Accordingly, it is desirable to provide techniques that consider the channel differences of different users and frequencies to optimize network resource allocation, and in an equitable manner, to increase the spectral efficiency and throughput of the network.